Process of electrically welding transverse plates to tubes



T. E. MURRAY. PROCESS OF ELECTRICALLY WELDING TRANSVERSE PLATES T0 TUBES.

APPLICATION FILED DEC. 16. I919.

Patented Aug, 24, 1920.

2 SHEElS-SHEET I.

T. E. MURRAY.

PROCESS OF ELECTRICALLY WELDING TRANSVERSE PLATES T0 TUBES. APPLICATION FILED DEC.16, 1919.

1 3 50, 8 3 3 I Patented Aug. 24, 1920.

2 SHEEIS-SHEE] 2.

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-' I water tubes, with the "conducting plates UNITED STATES PATENT OFFICE.

THOMAS E. MURRAY, 01 BROOKLYN, NEW YORK.

PROCESS OF ELECTBICALLY WELDING TRANSVEBSE PLATES TO TUBES.

Specification of Letters Patent.

Patented Aug. 24, 1920.

Application filed December 16, 1919. Serial No. 845,178;

Electrically l/Velding Transverse Plates to Tubes, of which the following is a specification.

The invention relates to a process of electrically welding transverse plates to the periphery of a tube. A product of said process is here shown embodied in a water tube steam boiler for the purpose of in-' creasing the 'heat conducting surface of the tubes therein.

In the accompanying drawings- Figure 1 shows a conducting plate in elevation having a recess and projections therein applied transversely to a boiler tube (shown. in section) before welding. Fig. 2 is a similar view, showing the tube and conducting plate after welding (part of Fig. 3 is a section on the line 3, 3 of 1. Fig. 4 is a section on the line 4, 4 of ig. 2. ig. 5 is a vertical section of a typical water tube boiler, showing the water tubes, and with the conducting plates thereon. Fig. dis a perspective view of a portionof one of the welded in place thereon. Fig. 7 is an illustrative diagram, showing current distribution welding.

Similar letters of reference indicate like parts.

It is desired to weld conducting plates transversely upon the tubes of a water tube boiler in order to increase the heat conducting surface of said tubes. In Fig. 5, I s

have illustrated a typical form of water tube steam boiler in which the tubes are shown at A, and at B the heating conducting plates thereon-said tubes, as usual, being disposed above the grate C, the products of combustion passing around and be-.

tween them to the uptake M. In Fig'. 6, I

show a portion of one of the tubes A in erspective, with the conducting lplates each ormed in two half sections D, said sections being disposed transversely on the tube, and having theedge of a curved recess in each electrically welded to said tube.

Considering one of said half sections, as D, I find that certain difficulties present themselves when theeliortis madeto weld the curved edge of the plate to the surface of the tube.' If the recess in the late be struck with the same radius as t e tube,

while it will fit thereon at the outset, the establishment of the welding current and the pressure exerted upon the plate in its own plane to forceit against the tube results in an unequal distribution of current.-

- Thus in Fig. 7 let it be assumed that section D is pressed downwardly upon the tube A. The pressure is exerted at arrow (1 in the line of a diameter of the, tubeat arrows b, b in lines tangent to the tube. As a consequence the metal fused at the outer portions F, F of the recess is not taken up as much as the metal at the middle portion G thereof, with the result that for as long as the current is ke )t on and the pressure continued, said middle portion is constantly eaten away, so that, as indicated by e dotted line H, a gap is produceibgm tn. the section and tube; while at the e time, the joints at the outer portions F, F of the recess are poor because of the necessarily small pressure thereat.

As the sole purpose of the transverse sections on the boiler tube is to increase the conducting surface and the union undergoes no strain, it is not essentially necessary thata perfect joint should be madeeverywhere between tube periphery and section, so long as the connection between the parts is suflicient to insure a proper amount of heat conduction. I find that this is not satisfactorily accomplished under the conditions of Fig. 7, and, therefore, the problem before me has been to devise a way in which a joint of ample conductive capacity can be produced with certainty, and every time. This is the invention herein -disclosed. I proceed as follows:

In the plate section to be welded I strike a senii-circular recess I of greater radius than that of the circular cross section of tube A,

and on the inner periphery of said recess I is eliminated, and in the meantime the other projections are also fused. The conditions are then substantially as shown in Figs. 2

and .4: that is, the fused metal of the proios tions of Fig. 1. I find that this union can be made practically instantly, without any special care in the welding, and that it is always of ample extent to obtain an adequate utilization of the heat conduction of the applied section. The number of projections in the section recess is not material so long as they provide suflicient metal to form said union in the period during which the projection J is being fused.

' I have described my method as applied to the welding of a single half section D. It

operates in like manner when the two half sections 1), E, similarly formed, are pressed and welded simultaneously upon opposite sides of the tube. The edges N, F said sections may at the sired, be welded together.

ig. 6, of same time, if dethat the projection J which, as I have said, regulates the period of operation, should have its radial direction coinciding with the direction-of the pressure; but in all cases the regulation is effected when the projection (the direction of which most nearly approximates the direction of the pressure) is fused.

I claim:

The method of electrically welding a metal plate transversely upon the circumferential periphery-of a tube, which consists in, first, forming in an edge of said plate an It is not essential arc-shaped recess of greater curvature radius than said tube having radial projections which make contact with said tube when said plate is applied thereto; second,,placing said plate transversely upon said tube and establishing the welding current while pressing said plate against said tube until the projection having its radial direction most nearly approximating the direction of pressure becomes fused.

In testimony whereof I have aflixed my signature in presence of two witnesses.

THOMAS E; MURRAY. Witnesses:

GERTRUDE T. PORTER, MAY T. MCGARRY. 

